The plan, estimated to cost at least HK$624 billion ($80.51 billion), or close to a quarter of the city’s gross domestic product, would be Hong Kong’s most expensive infrastructure project, and would cover an area about a third of Manhattan’s.

The project has drawn criticism both on cost grounds and for its possible environmental impact.

The studies, which will take 3.5 years, are worth HK$550.4 million.

Secretary for Development Michael Wong told lawmakers that not all of the HK$624 billion would be covered by public funds and that the government expected to earn an income of at least HK$707 billion from land sales on the artificial islands.

The approval came swiftly after pro-democracy lawmakers, who opposed the plan in previous years, quit the legislature en masse earlier this month in protest against the ousting of four of their colleagues after Beijing granted the government powers to disqualify lawmakers without court scrutiny.

Activists have said it would cause irreparable damage to marine life and other ecosystems and argued it would be much cheaper for the government to acquire unused brownfield and agricultural land from private developers and investors.

Discussions on the Lantau Tomorrow Vision, which was first announced by Lam in her policy address in October 2018, had stalled, with the legislature paralysed by anti-government protests.

Last week, Lam said in her latest policy address the reclamation project “is practicable and will bring enormous economic benefits to Hong Kong”, urging the public to look at it in an “objective and fair manner”.

The initial phase of the project, which spreads across 1,000 of a planned 1,700 hectares of reclaimed land between the Lantau and Hong Kong Island, will build up to 260,000 housing units.

Wong said the Lantau Tomorrow Vision aims to start reclamation work in 2027 and have the first batch of residents to move in by 2034. It will also have a third core business district.

($1 = 7.7506 Hong Kong dollars)